2003 Public Awareness for Carlsbad and San Luis Rey
    Watersheds (Report and Appendix) (8/03)
 

The San Luis Rey River watershed is located east of the City of Oceanside in the northwestern portion of San Diego County.  The 558 square mile drainage is the largest hydrologic unit in the San Diego region.  The watershed drains to the Pacific Ocean to the west and is bounded by the Moserate Mountains to the north, the Cleveland National Forest and Camp Pendleton to the northwest, and Escondido, San Diego, and other cities to the south.  The basin is roughly 50 miles long by 16 miles wide, and is divided into two hydrologic units by Henshaw Dam.  The areas above and below the dam encompass 206 and 354 square miles, respectively (USACOE, 1977).

Approximately 92.5% of the San Luis Rey River watershed is located in unincorporated areas of San Diego County.  Roughly one-fourth of the land area in the watershed is located west of Interstate 15 including portions of the cities of Oceanside and Vista, the communities of Fallbrook and Bonsall, and the southwestern portion of Camp Pendleton.  The land west of I-15 has multiple uses including open space/ undeveloped, residential, commercial/ industrial, and agricultural.  East of Interstate 15, most of the land is owned and managed by government agencies (county, state, and federal), special districts, and Native American bands.  The predominant land uses are open space/ undeveloped and agricultural.

Unlike most major rivers in Southern California, the San Luis Rey River has undergone relatively little channelization.  The only significant segment of the river that has been channelized is within the City of Oceanside.  However, the cumulative impacts of various land use practices in the basin appear to be degrading the river’s environmental value.  For example, an increased rate of bed erosion attributable to sand mining operations has been observed in the central reaches of the river.

There are many beneficial water uses within the San Luis Rey Watershed as designated in the State Water Resources Control Board's San Diego Region Basin Plan.